Load Cell Fault Finding – Part 1

We often get asked for fault finding tips and so I’ve put together a simple fault finding guide for a load cell system.

The output from a load cell is tiny! Any small interference will show up and then be amplified by the signal conditioner. The longer the cable the greater the interference will be due to increased coupling.  It will be improved if screened, twisted pair cable is used as with a good quality signal conditioner this will allow a lot of noise to be removed.

A certain amount of physical noise is normal, especially in very sensitive load cells. This can be from all sorts of sources ranging from computer fans on the same desk as the load cell to fork lift trucks driving around on the floor above! The more sensitive your equipment, the greater the degree of separation that is required from the rest of the world!

In figure 1 below, we can see a diagram of a load cell system.


Figure 1.  A load cell system

For this guide I have decided to split the fault finding into the areas load cell, signal conditioner and cabling.

I’ll start with the load cell…

Check correct wiring connections and colour coding

The first thing that I’d check is the wiring connections between the load cell and the signal conditioner. The colour codes vary between manufacturer and it is best not to assume anything. Usually the colour coding is on the load cell’s calibration certificate. Ensure that the wiring is as described. Getting this wrong can give inverted or biased results.

Check load cell resistance between excitation +/- and signal +/-

Also on the calibration cert should be the resistance between excitation +/- and also between the signal +/-. Measure those resistances with a multimeter to confirm that there is no internal damage to the sensor. (There will be a little variation from the figures stated on the calibration and this is normal). Don’t forget to disconnect the load cell from the signal conditioner before doing this.

Check for mechanical restriction on load cell movement

Have a good look at the load cell. Is it free to move? Any mechanical restriction will have an effect on the load cell’s output. (You can also use this phenomenon to limit the total movement of the loadcell to prevent accidental overload). Even poor cable routing can twist a small load cell and give skewed readings. Therefore it is important to make sure that the cable routing is free from any strain. Also the weighing vessel needs to be free to move in the direction of the load.

Check to see if load cell has been overloadedosbst-200x200

Another possible problem is if the load cell has been overloaded. A small load cell could have been overloaded simply by leaning on it. If this has happened it may have permanently deformed the load cell and it will not return to its zero position correctly. This is likely to show as a non-zero reading under no load. There is a high chance that this will be terminal! Talk to your load cell manufacturer for more information.

Now we can look at the load cell cabling. As previously mentioned, the voltage outputs from the load cell are very small and easily influenced by the outside environment. There are several ways of minimising the disruption.

Keep distance between load cell and signal conditioner to a minimum

The further apart the load cell and signal conditioner are, the more susceptible the cabling is to capacitive coupling and electromagnetic fields. Keep this cable short and there will be less interference.

Keep all sensor cable runs away from inductive loads

It is very good practice to ensure that all sensor related cables including sensor power are kept separate from any inductive loads and their power feeds.

Ensure that you are using twisted pair, screened cable

Using twisted pair cable can help reduce the magnetic influence of power cables. This needs to be in partnership with a signal conditioner’s common mode rejection capability. Screened cable prevents capacitive coupling by coupling to ground instead of the signal wires.

Check cable is screened and only connected to ground at one point

If the screen is grounded at more than one point a ground loop is created. This is the cause of the earth hum in audio systems. This is just as problematic in instrumentation systems. Remove any extra link(s) between screen and earth. DO NOT disconnect the earth wire of the appliance in question. This is dangerous and can cause serious injury.

Test cable continuity

A simple continuity test can check the integrity of the cabling. Disconnect the cable and check the resistance.
In the next post we will discuss the signal conditioning part of the system….

By Tom Lilly, Technical Support Operator at Mantracourt

Continue to Load Cell Fault Finding – Part 2

A Marketing Intern’s Perspective

My name is Konstantin Delov and I’ve been part of the Mantracourt Marketing team for almost half a year now. I spent my summer working on improving our online presence and supporting our network of technical partners in the promotion of our products. I was fortunate enough to be around and participate in the preparation of two of our product launches – both T24 and BroadWeigh Updated Range.

In the next few lines, I’d like to reveal a unique side of Mantracourt that very few people can see, along with a short story on my participation at an international innovation competition.

Behind every great achievement stand a number of strong supporters. People’s attention is often focused on the final result, but that doesn’t diminish the importance of the bits that quietly, but consistently contribute to it. Just like our signal interface solutions that support a variety of industries, often remaining unnoticed.

A few months ago, I heard that same monotonous buzz indicating an incoming email. Though the content of the message was a bit more special than usual. I was being notified by Microsoft corporation that me and my Exeter University team had reached the World Wide finals of the biggest student competition there is – The Microsoft Imagine Cup. I was going to visit their HQ in Redmond, Seattle, play with HoloLens and pitch to some of the most influential figures in the corporation.


Sounds exciting, but it’s not the type of trip that you just go to. It tested our limits as a team and individuals, required us to burn the midnight oil on a frequent basis. It involved thorough planning and outstanding discipline. Selling an idea is not among the easiest of things.

Fortunately, the work paid off and my team became third worldwide in the innovation category!


And yes, it might have been me filling out the quotes for the press releases and smiling for the photos but, once again, without the skills that I had gained at Mantracourt things could have looked way different. The company taught me consistency. I managed to get a close look of how an organisation with worldwide distribution gets its message across and reaches its sales targets. You can’t simply learn these lessons in a lecture theatre.

In this day and age, Mantracourt is a rare example of a company that doesn’t just blindly follow numbers. It is a place where every employee, customer, supplier or contractor is respected as a valuable part of a team, rather than a production or sales robot. And this pays off. Every piece of electronics that comes out of our factory is manufactured and tested by people who want to see the company thrive. Every board that we sell is sought and needed by the customer. We always make sure that it will genuinely help them towards achieving their goal, be it for project or distribution purposes.

By Konstantin Delov, Marketing Intern at Mantracourt

Why Go Wireless?

There are many good reasons to switch to wireless for your sensor requirements. It almost seems an easier question to ask ‘why not?’ but I’ll start with ‘why?’

The Benefits…

The first, most obvious plus for wireless is the lack of wires!  With moving loads, trying to keep the cables neat, tidy and unbroken can be a pain. Depending on the installation, replacing damaged cables can be very tricky, time consuming and expensive. Fault finding on complex systems can also be very time consuming.

With a wireless system the initial installation process can be very quick and easy. Wireless sensors can be moved to different places if continuous monitoring is not required, saving costs.

All our transmitter modules can run on batteries, also removing the need for power cabling. Depending on sample time and frequency battery life of up to 5 years is achievable.

Devices can be easily swapped out if required. It is even possible to change the data tag of the new device to match the one being removed so none of the receivers need to be changed.

Extra devices can be easily added to the system. Only requiring simple reconfiguration of receiver devices.

Wireless Issues and How We Address Them

People often worry about the security of their data. When sending data wirelessly anyone with the correct receiver could also be picking up all the data. Fortunately we have a way around this with Group Keys. Once a Group Key is set, only devices using the same Group Key can ‘see’ the data from that device. (The Group Key offers millions of different combinations).

Another concern can be about interference from other devices. Firstly, due to the T24 error checking, if data is being displayed, it will be the correct data. There is a possibility that other radio traffic could interfere with T24 transmissions and we therefore provide within our Toolkit a spectrum analyser to check radio traffic on the 2.4GHz frequency band. If heavy traffic is discovered simply switch to a less congested channel.

Before installing any system it is important to test that it is correct for your uses. Our T24 Toolkit allows for monitoring of radio signal levels at both the device and the base station to allow full analysis of variation with movement and other environmental factors.

For our testing we use an open field site with the transmitter 3 m above ground and the receiver at 1.5 m above ground. Increasing either height will generally increase the range. Any obstacles within range will affect how the radio propagates and will change the range and coverage.

It is also worth noting that the positioning of the components that make up any wireless telemetry system always involves a degree of experimentation.  Time spent on this aspect will always ensure a successful outcome.

By Tom Lilly, Technical Support Operator at Mantracourt

Tom’s Tech Tips

The T24 data logging software and data mapping software is now available to download free of charge.  Tom Lilly, Technical Support Operator at Mantracourt, talks us through this intuitive application…

The full functionality of T24LOG100 is now available to anyone that wants it at no cost. It means that people can have a proper experiment with an important part of a system without any expenditure. This should allow people to discover how useful and easy the T24 system is. You don’t even need a base station to have a look through and change the sample projects. The tooltip help and main help files are really useful for getting to know the software.

T24LOG100_Montage-webAll the functionality is there.  We have up to 100 channels of display and data logging, trend charts, mapping functions allowing intuitive visual displays, report generation and web server function for viewing on multiple platforms all over the world!

What do we mean by 100 channels?  Well, these channels can either be T24 transmitter modules or mathematical functions based on the transmitters and/or other display channels. Each channel has the option of setting a peak or valley hold or varying filtration levels. All display channels can also have warning, underload and overload levels set.

All the display channels can be logged to a csv file. This can be triggered manually or automatically at intervals and opened in spreadsheet software such as MS Excel.

Double clicking on any of the display channels shows detail about that channel including a trend chart with up to 10,000 data points.

The mapping function gives the possibility of creating intuitive displays needing very little explanation. Image files such as JPEG, PDF and DXF can be imported and other objects such as status icons, level indicators and displays can be placed on the page. With some clever thought, items can T24LOG100_Web_Server-webbe made opaque at certain levels and clear at others allowing the images to change as the load state changes. Up to eight pages of display mapping can be used. As previously mentioned, the example project has some useful demonstrations.

Reports can be generated and saved or printed when required. These can be in various pre saved formats.

Finally, my personal favourite is the web server. With this we can see a simplified version of the main display page in a web browser. This then means that if we know the IP address and password we can view this info on any computer, tablet or smartphone connected to the same network as the host computer. It is also possible that we can dial in from anywhere in the world to see the displayed data.

As well as the demo projects with the data logging software we now also have the first in a series of demonstration videos on LOG100. This can be found on the Mantracourt YouTube channel – click here to view.

By Tom Lilly, Technical Support Operator at Mantracourt


Meet the Team – Manufacturing Team Leader

Tracey Richards, Team Leader of Mantracourt Manufacturing talks about how quality is integral to her role and how her electronics career has taken her from photocopiers, to military equipment, to industrial instrumentation.

I will start off by telling you all a bit about myself. I have been at Mantracourt since 2011. When I started, my role was to be the team leader for our standard product line of instrumentation and I am now the team leader of the Mantracourt manufacturing team. There are 12 people in our team.

I am responsible for the quality of products leaving Mantracourt.  Also, sub-assemblies we receive from our suppliers, training, day to day running of the department, manufacturing instructions, equipment and new procedures and techniques that become available.

Most of my working life has been in the Electronics Industry. My first job was at Rank Xerox, Welwyn Garden City. Although I was to be working in manufacturing, I had a two week training period. It was spent in a training room and we were not allowed to touch any product during this time. In truth it was a good job too. The programme for us was to learn how to identify components, resistor colour codes, component values, rework, track and pad repair, which has always come in handy and modifying PCBs. When leaving Rank Xerox, I went to work for Hocking Electronics NDT. Here I learnt how to wire wind probes and work to MOD standards. As I continued my working career I always went somewhere where I would improve my skills and knowledge. I can work to IPC-A-610 Class 3. My experience comes mainly from working in the Military, Medical and Aerospace industry.

The training of team members at Mantracourt is of the highest standard and we work to IPC standards Class 2.  I undertake all training to staff on an ongoing basis as and when new techniques change.

I encourage the team to learn from each other.  We regularly talk about processes and lessons learned and ideas for regular reviews.

We operate a Quality Management System where all equipment has to be documented and records of calibration and any testing that has taken place is stored. Drawings, tests, rework, are all recorded.

We have regular internal audits, which includes ESD (Electrostatic Discharge) checks to benches and floors, which are checked monthly.  A personal ESD check, which includes correct footwear and the use of wrist straps, are done on a daily basis.  I make sure everyone is working within a safe environment.

At the end of the SMT (Surface Mount Technology) line we have an AOI (Automatic Optical Inspection) machine that most of our products go through.

This inspects the boards for misplaced components, dry joints, correct orientation and correct component ID.

We also carry out visual inspection on all products to check the final quality before shipping.   We take quality very seriously and as a team leader, maintaining quality is my most important job.
We are ISO9001 certified and manufacture ATEX approved and RoHS compliant products.

Here are some interesting statistics. The team and I are very proud of what we achieve.

  • Our production yield is 99.96%
  • First time pass rate over total operations 98% (where a single product may include 10 or more operations)
  • Scrapped 0.04%
  • Product returns due to manufacturing issues – quantity 5

2012 / 2013 statistics”

Manufacturing is a precise business and I am very proud to work with such a great team that help to produce the high quality products that we are renowned for.  For me personally, and this is what I ask my team to keep in mind – if you were going to buy one of our products with your own money, would you buy it?
Even though I don’t deal directly with our customers their requirements are first and foremost.

On a closing note, one of my team members overheard a conversation I was having with Rebecca in the sales department. At which point he said to me I had made two statements, one of which was impossible and the other which was totally true. The first statement was, “Just ignore me Rebecca” he said that’s impossible to do. The second statement was “I don’t know Rebecca” he said now that’s true.   I suppose I can’t always be right…well not all of the time!

By Tracey Richards, Team Leader at Mantracourt

Did You Know About The Handy Battery Life Calculator?

Always keen to provide helpful tools to assist you, our design engineers have produced a clever tool to predict how long the batteries will last in the acquisition module of your T24 wireless telemetry system – the Battery Life Calculator

By simply selecting the required module and inputting your chosen variables into the calculator, you will be able to obtain a prediction of the expected battery life.

Click to open the Battery Life Calculator

By Dave Porter, Technical Sales at Mantracourt

Manufacturing Talent

My name is Fabian and I am twenty years of age.  I started working at Mantracourt Electronics in November 2013 as an Electronic Manufacturing apprentice.

When the opportunity came along to start an apprenticeship at Mantracourt I jumped at the chance.  I have always been interested in technology and had worked on my own projects in my spare time, including fixing resisters and capacitors on iphones, PC’s and gaming consoles.  To have the opportunity to do something that interests me where I could work and train at the same time with good job prospects was a dream come true.

When I first started, one of my first tasks was to learn the basics of soldering different types of retrofit components and surface mounts components.  Although a little daunting at first, this was a skill that I picked up very quickly.  I also learnt how to rework circuitry; this is a particularly useful skill for moving components, if needed.

I started practising on scrap boards until my team leader decided that I was competent enough to work on products.  This was really exciting because when a board that I soldered passed test for the first time, my team leader was very impressed and I felt proud of myself.

I was also taught about the effects of Electrostatic Discharge (ESD) and how to prevent it in the workplace.

A month later I was learning a lot of new skills, such as how to use the EBSO machine (selective soldering machine).  This was a great privilege because only certain people are trained on this and it felt great to have importance and responsibility in a job.

I attend college once a week and am studying maths and science.  I also learn about how to work with machines and different types of tools in the workshop.  The workshop lesson is my favourite aspect because I am learning skills that are really useful at Mantracourt and compliment the in-house training that I receive.

The best thing about working at Mantracourt is the fact that I am learning new skills and I have finally discovered something that I’m good at and enjoy, and the bonus is I get paid for doing it!

It is also so rewarding to see the end results of a product that I have spent time on, finished and working and ready to go off to our customers.

As an apprentice I will get the opportunity to work in all aspects of the business, including  sales, marketing and with the design engineers.  There is a great team of people here.

As part of the in-house training and education I have worked with various products from our standard product range.  An example is the SGA/D, which is a high performance signal conditioner, for use with strain gauges.  It offers a wide bandwidth and a wide input signal range.

Let me explain the processes this item goes through in basic terms…

This product starts by going through the SMT Line (surface mount machine), this puts all the surface mount components in their correct places.

The next step is a high speed visual inspection by a machine that checks that each component is correctly located, checks for the integrity of the solder joints and can also identify if any component has an incorrect value.

Once this is done it is moved over to the EBSO machine.  This is where all the retrofit components are put into place and soldered with a small ‘wave’ of solder.  The correct nitrogen levels are essential.  We put four of these boards through on each run, and each run takes about 12 minutes.

For every operation that is undertaken on the product you must mark off on the Product Database which stage it is at and how many products have been through this stage.  This means that once the boards have been through the SMT line they must be marked off and inspected.

After the boards have been through all of the assembly processes it’s time for them to get tested.

All products undergo rigorous quality testing and we have different methods of doing this, but they mainly undergo testing by the automatic test equipment system (ATE) using various jigs.

Once the SGA’s have passed the ATE test they are then put into their respective cases and are transferred to the dispatch department, where they are put into stock, or packaged and sent off to our customers.

I think the biggest challenge for me so far has been learning all of the different component names and learning where each component is stored.  This took some time but now I am familiar with these…it’s just like riding a bike!

My goals for the future are to learn how the entire organisation works, and to have first-hand experience of every aspect of the company.  I would love to get involved with product design and create my own product for the company one day…. watch this space!!!

By Fabian Gilson, Electronic Manufacturing Apprentice at Mantracourt

Highlights of the T24 Logging Software

I have had a lot of enquiries recently asking about our T24LOG100 software and how it can work for them, so thought this a good opportunity to discuss the main aspects of this incredibly smart piece of monitoring technology developed in-house by Matt Nicholas our IT and Software Guru.

The latest version of our T24LOG100 instrumentation monitoring software includes advanced features such as a graphical / mapping capability and a facility for remote viewing via a web server.


A variety of image formats including PDF, JPEG and DXF can be imported to incorporate into your project. This innovative application facilitates a real-time monitoring system with simultaneous displays of load cell data presented as graphics on a visual representation of the structure on which the sensors are located.

This display features “drag and drop” placement of customizable readouts, warnings and user definable “buttons” to toggle between pages, reset alarms etc.  The use of a graphics background for the application offers a system which has the advantage of allowing a more intuitive and accurate response to the management of multiple and interacting loads.

Up to eight pages can be defined and you can switch between pages. Clicking displayed values, which can be in the form of digital display or bars, takes you back to the ‘zoomed in’ view so you can quickly investigate values.

Web Server

The T24LOG100 software now has a built in web server to provide a summary view page to other computers, tablets, iPads and smartphones etc using a standard browser. This summary page shows all channels and error and alarm status.

The new web server facility enables users to view the data online wherever they have access to their network. Users now have the freedom to monitor sensors and installations when on the move and on-site.

The built in web server also allows you to add your own custom web pages.


T24LOG100 software is a data logging package that can handle up to 100 channels of wireless instrumentation data simultaneously whilst also offering a range of sophisticated features that will enable users to optimise system monitoring.

You can ‘zoom in’ on individual display channels to view detailed information on that channel along with 10,000 points of historic data.

The T24LOG100 display is customisable and it can be branded with company colours and logo and licenced for distribution.

Certain versions also come with the option of royalty free distribution to your customers.

If you have any questions please do not hesitate to contact me.

By Dave Porter, Technical Sales at Mantracourt
Tel: +44 (0)1395 232020

The Sky’s the Limit – Highlights from the Past Four Decades at Mantracourt Electronics

2014 marks the 40th anniversary for Mantracourt Electronics and throughout this year we will be delving into the archives to share with you some of the highlights from the past four decades.

From our humble beginnings, which started life in a garden shed to the 3,600 sq ft manufacturing facilities we now occupy, we have supplied measurement instrumentation to some very well known and innovative projects.

One such project came along in 1985 and involved NASA’s Space Shuttle Programme.  A temperature and humidity monitor supplied to Solomat, another East Devon company at the time, was supplied to Honeywell and used in a satellite which was carried by the space shuttle.

The story is captured in the article below and tells the tale of our beginnings and of the project.

“Into Space from East Devon” – Wednesday, 31 July, 1985 (Source: Express & Echo)

We hope to post some more articles and photos from our archives during this anniversary year to entertain and inspire! Follow us on FacebookTwitter and LinkedIn.

Designing Accurate Amplifiers for Tiny Signals


Designing instrumentation electronics for the amplification of small signals can present a number of challenges. Whether it is the electrically noisy world we live in, or our expectation that the equipment will work reliably under the bonnet of a car or in the North Pole, ‘real world’ electronic design is rarely straightforward. This blog discusses a few important design issues that impact upon the development of high quality instrumentation amplifier and signal conditioners.

Ron Joyce, Design Engineer at Mantracourt explains more.

Amplifier Design

The starting point of such an amplifier design may well be the choice of Operational Amplifier (op-amp) for the input stage. There is quite an array to choose from but choosing a device that offers a first gain stage with a low offset drift and low noise performance is crucial if the signal quality at the input stage is to be maintained.

To further ensure signal stability, the ‘gain resistors’ within the op-amp circuit should be high quality components and have a temperature coefficient of 5ppm/°C or less.

Where potentiometers are incorporated in the design to enable the amplifier to be calibrated, the range of trim they provide should be optimised for ease of calibration and to minimise the effect of their temperature coefficient which, by contrast could be 100ppm/°C or higher. There is a trade-off between allowing enough adjustment to compensate for transducer and electronic component variation and reducing the effect of the potentiometer’s relatively poor temperature stability in the signal chain. In practice the potentiometer should provide only the minimum amount of adjustment necessary to overcome the system variables, any more than this degrades the temperature performance and makes calibration difficult to set due to the excessive amount of adjustment on offer.

PCB Design

A ground plane is an important feature when designing a PCB for a small-signal amplifier. This comprises a layer of copper that serves as a low impedance return path for the currents flowing from various parts of the circuit. This helps to reduce noise and ensure that all components within a system use the same reference potential when comparing different signal voltages.

A ground plane also facilitates PCB design, the ground connection of any component can be directly routed to the ground plane by means of via holes without having to run additional tracks.

In a similar way to the ground plane, when adopting a multi-layer approach, an internal power plane can be incorporated into the PCB design. Power planes can be placed on adjacent layers to ground planes creating a large parallel plate capacitor that helps to filter the power supply.

The use of ‘guard tracks’ is recommended to reduce the effect of PCB leakage currents. The guard track surrounds a sensitive, high impedance area of the circuit (often the input pins of an op-amp) and is connected to a low impedance source at the same potential. Since there is no potential difference between the guard and the sensitive area no current flows and a barrier is formed to any leakage current across the surface of the PCB.

Every PCB design includes unintended thermocouple junctions which modify the signal voltage due to the sum of the thermoelectric voltages generated. Such junctions are formed by two dissimilar conductors for example components soldered to copper pads, wires attached to PCBs etc. To lessen the effect, temperature gradients across the PCB should be minimised with the use of heat sinks and critical components should be grouped tightly together. Even the orientation of individual components should, where practical be taken into account by ensuring that their soldered ends are perpendicular to the direction of heat flow. Any thermoelectric effect will then be cancelled out.

Another approach is to thermally isolate certain components by including routed slots or paths in the PCB. The goal is to create nearly constant temperatures in critical areas.

PCB tracks that are carrying low voltage signals should be routed with care, avoiding noise sources. Track clearances and widths should also be considered.

Finally, with regards to the PCB layout, it is important to observe good EMC procedures.

EMC and Enclosure Design

For the accurate amplification of tiny signals, stray radio frequency signals need to be eliminated. The main problem is that unscreened high-gain amplifier circuits tend to act as radio receivers, picking up the radio frequency signal on resistor legs and PCB tracks etc – then amplifying them along with the instrumentation signal. This stray RF may be generated by electric motors, transformers or even electric lights.

For this reason LC low pass filters should be included on all I/O lines and PCB tracks should be kept as short as possible. The use of surface-mount components helps in this respect.

Ideally, a fully enclosed metal enclosure should be used to house the signal conditioning module with cable entries via EMC glands. If using a plastic enclosure, then some form of internal screening should be implemented.

Naturally, all wire connections to the amplifier will need to be screened, especially on the input otherwise these wires will simply act as antennas.


Careful choice of components and thoughtful PCB design are the main factors to consider in the design of low noise, low signal level amplifiers. 

Written by Ron Joyce of Mantracourt

Mantracourt is a UK based company that specialises in the design and manufacture of instrumentation amplifiers, load cell signal conditioners and wireless instrumentation systems.

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